Do Italian wines shipped to the U.S. contain more sulfides than the bottles sold in Italy?

Hello there! I'm Dr. Vinifera, but you can call me Vinny. Ask me your toughest wine questions, from the fine points of etiquette to the science of winemaking. And don't worry, I'm no wine snob—you can also ask me those "dumb questions" you're too embarrased to ask your wine geek friends! I hope you find my answers educational, empowering and even amusing. And don't forget to check out my most asked questions and my full archives for all my Q&A classics.
Dear Dr. Vinny,
Do Italian wines shipped to the U.S. contain more sulfides than the bottles sold in Italy?
—Linda, Altoona, Pa.
Dear Linda,
I think you mean sulfites, not sulfides, but I thought I’d use this opportunity to remind you and others of the difference between the two. Sulfides are volatile sulfur compounds and, while harmless, are typically considered a flaw because of the stinky, skunky or rotten egg–like aromas they can contribute to wine. Sulfites are a naturally occurring byproduct of wine, and sometimes winemakers choose to add additional sulfites to prevent a wine from spoiling.
Wines sold in the United States have the “contains sulfites” note on wine labels, but wines sold in Italy do not, simply because labeling laws differ from country to country. So the same wine—with the same amount of sulfites—will or won’t carry that warning, depending on where it is sold. Italian wines imported to the U.S. have to have this “contains sulfites” wording on their labels before being sold here.
For most of us, sulfites aren’t a problem, and are part of many things we consume, like dried apricots, molasses and blue cheese. But for the approximately 1 percent of people that have sulfite allergies, wine can be a concern, and cause some scary reactions, from wheezing and asthma-like attacks to digestive issues and difficulty swallowing.
—Dr. Vinny